const user = {
    username: "张三",
    age: 19
};

const isAdult =  (age) => {
    if (age > 18) {
        console.log("成年人")
    } else {
        console.log("未成年")
    }
}

// export 将别人要使用的变量和方法导出
export {user, isAdult}